Underwater Archaeology in Bermuda

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Holding it all together

Warwick lies, torn asunder, on the floor of Castle Harbour. As we slowly uncover the ship’s buried skeleton, we are continuously astounded by the quality of her construction. She was built from densely packed, massive oak timbers. Between three layers of outer planking, frames, and inner planking (confusingly referred to as ceiling), Warwick’s hull would have been solid wood, two feet thick in places. It is incredible to contemplate the forces required to rip her apart, and partly explains why a large section of her starboard side is still intact and well preserved.

Seventeenth Century English vessels were held together with heavy wooden pegs called treenails (pronounced truhn-el, as in trunnel). You can see them sticking up out of the frames where the planking has come away. Where only outer planking remains, you determine the position of frames by looking for rows of treenails.

Treenails are powerful, rust free fasteners. A carpenter would first drill a hole through an outer plank, the frame and an inner plank. They then drove a long, tapered wooden peg (the treenail) into the hole as far as it would go and cut off the protruding ends. When immersed in water, the treenails expand and lock in place, sandwiching the frames and planks together.

Often, carpenters split the end of the treenail with a wooden wedge, driving the sides apart and locking it firmly in the hole. It is very difficult to see these wedged treenails under water. You have to carefully look for changes in the grain to identify the wedge – though sometimes you are lucky, and dust fills in the minute cracks, rendering them visible.

Sometimes repairs are obvious. They might be fastened differently, a different type of wood, or cut across several planks. Most are more subtle , and treenails can help identify them. Wedging is a good clue. Carpenters either used a square peg, wedge or crossed wedge to expand the head of a treenail and lock it in place. The style that was used depended on the situation, and where the shipwright was from.

To determine where repairs are, you have to understand the construction sequence first. When you see a treenail driven through the center of a second treenail, you know that one was in place before the other. This might mean that one layer of planking was attached to the frames, and then a second, or it might mean that they decided to put in a second fastener. It might also indicate a later repair. It could be many things.

The same is true if you find cut off treenails beneath the ceiling (inner) planking. If the shipwright fastened the ship’s outer planking first, they would have to cut off the protruding treenail ends before laying the inner planking. In other circumstances it might indicate a repair, where ceiling planking was removed, protruding heads adzed flat, and new plank put in place.

In almost all circumstances, you have to look at a broad range of data, think about the construction sequence and look for things that are out of place. On the other hand, if you are an expert like Jon Adams or Kevin Crisman, you just look at it and know.

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EXPLORE HISTORY:

For an extraordinary dive into the island's past, visit National Museum of Bermuda. Home to 500 years of history, the museum is located in the citadel keep that towers over the historic dockyard district. Whether you are interested in seeing relics raised from shipwrecks, learning more about the forts that once protected the island or want to explore early colonial history, there is something for everyone.

If you are interested in diving on some of Bermuda's most incredible wrecks, try the Tucker's Point Dive and Water Sports Center. Over the centuries, hundreds of vessels have fallen victim to Bermuda's beautiful reefs. Diving on them is an unforgettable experience - and we go out any chance we get!

Explore other shipwreck excavations around the world with the Institute of Nautical Archaeology! We are working in Bermuda, Brazil, Canada, Italy, Japan, Jamaica, Spain, Sri Lanka, Tobago, Turkey, Ukraine, and United States - so check out our other blogs!

The GEOS Foundation supports geographical research and scientific expeditions around the world. Follow reports from the field on the GEOS blog.